Agon. The Goldberg Variations. In the Upper Room. We hear these titles today and think, “Classics.” But at what point does a ballet achieve that status?

For Peter Boal, when the ballet was Alexei Ratmansky’s Concerto DSCH, almost instantly. “I had a really strong reaction to that work,” says Boal of first seeing DSCH at New York City Ballet, shortly after its 2008 premiere. “It felt as fresh as some of the Robbins premieres that I’d seen, some of the Balanchine premieres I’d seen. It tapped into humor. It had strong classical technique and elements of experimentation. It used the ensemble incredibly well. I felt like I was seeing one of the greats unveiled.”

It wasn’t long before Boal, the artistic director of Pacific Northwest Ballet, brought the brisk, bright, architectural work to PNB, presenting it on a mixed bill titled Contemporary 4 in 2011. The Seattle Times critic Moira Macdonald greeted the program with a simple request, echoing the rave reviews that DSCH had received in New York: “More Ratmansky, please.”

Every generation has its classics. Ratmansky is one of a handful of contemporary choreographers making ballets that, if their rapturous reception and increasingly global presence are any indication, might prove to be the classics of tomorrow. Right up there with DSCH—which, in addition to its Seattle run, has traveled overseas to the Mariinsky Ballet and La Scala—are Christopher Wheeldon’s Polyphonia and Wayne McGregor’s Chroma. Fourteen companies in six countries, have acquired Polyphonia since New York City Ballet first performed it in 2001. Chroma, which premiered in 2006 at The Royal Ballet, has entered the repertories of San Francisco Ballet, the Bolshoi Ballet, Royal Danish Ballet, National Ballet of Canada, Boston Ballet and, most recently, Alvin Ailey. Whether we’ll call these “classics” decades from now remains to be seen. But at the very least, as Ib Andersen, the artistic director of Ballet Arizona, puts it, “They have legs.”

Which raises a simple question: Why? What accounts for how widely these ballets are performed, for their appeal to artistic directors in search of new repertory? Is it some objective “greatness”? Or more practical assets, like the ease and efficiency of producing them? Is it the excitement they bring to audiences, the artistic challenge they offer dancers?

In the case of Polyphonia, all of the above. At once strident and playful, the 10-section work, set to Ligeti piano pieces, shuttles eight dancers between demanding solos, duets and trios. The costumes are spare—a nod to Balanchine’s “leotard ballets”—and the set nonexistent, save for a muted backdrop, letting the eye focus in on the blade-like mechanics of the body. As Wheeldon says, “It’s low on production and high on dance, which makes it easy to stage yet a rich experience for both audience and dancer. Plus it offers eight dancers soloist roles.”

And not just any roles, but richly layered ones: “Each dance has its own little story,” Wheeldon adds, “so it demands dancers with a great sense of theater and imagination in order to transcend the technical demands of the choreography.” He observes that the ballet “seems to take pleasure in new interpretations. It allows the individuals to shine and their own personal character to come out.”

“It has good bones,” says Andersen, who brought Polyphonia to Ballet Arizona in 2009. “It’s structured in such a way that your mind keeps itself busy. It is not so predictable—there aren’t many choreographers who are not predictable after a while.”

That sense of invention also impressed Boal, who brought the work to PNB—the company’s first taste of Wheeldon—in 2007. “It’s interesting when you feel like you can see the world in just eight bodies,” Boal adds. “Polyphonia really runs a gamut of expression and unexpected form. You think there’s only so much you can do with two legs and two arms, but Chris came up with a whole lot more.” Like Wheeldon, he notes that the ballet “wears its multiple casts well,” suiting new dancers as much as its original interpreters.

McGregor’s Chroma, with its barely-there beige costumes and austere set by the British architect John Pawson, may also seem “low on production”—but deceptively so, says Helgi Tomasson, the artistic director of San Francisco Ballet, which gave Chroma its U.S. premiere in 2011. “You can call it minimalist,” Tomasson says of Pawson’s set, which frames the stage with three towering white walls, one open at the back to serve as an entryway for the 10 dancers. But despite the “linear and clean” aesthetic, he explains, “it’s very complicated to put up.”As, too, is McGregor’s famously pliant choreography, which prods the body into creaturely realms, often thrusting dancers into sensuous confrontations. “He really challenges and stretches the dancers, bends them—you name it,” Tomasson says. “He has them going into positions that, again, we don’t normally see the body going into—like a rubber doll sometimes.”

“It’s not easy dancing, and it took them a little while,” he adds, referring to the dancers cast in the piece, “but they got it.” Joby Talbot’s clashing, brass-heavy score was difficult in a different sense: not something that Tomasson would “sit down and listen to on its own,” he says. Layered with McGregor’s preening, elastic movement, though, it clicked: “I felt the score fit very well what he was doing. They came together.”For the moment, Chroma, Polyphonia and Concerto DSCH have a broad appeal—which also stems from what they offer even the most accomplished dancers: a steep challenge. But for Tomasson, the term “new classic” inspires some skepticism. “It’s fantastic. It’s very now,” he says of Chroma. “Will it be very now in 20 years?” Andersen takes a similar stance. What makes something a classic? “Time,” he replies. “Time, time, time.” Siobhan Burke is a New York dance writer. She contributes frequently to The New York Times and Dance Magazine.